In general, terminal-crimped wires used for production of wiring harnesses are prepared by stripping an end of a coated wire and then crimping a crimp terminal to the stripped end of the coated wire. The crimp terminal includes a wire barrel portion formed integrally therewith and to be crimped to a core wire of the coated wire, and adapted to electrically connect a terminal portion of a connector housing to the core wire through the wire barrel portion.
The process sequence of fabricating the terminal-crimped wire is automated by an automatic wiring assembly fabricating apparatus. For example, the automatic wiring assembly fabricating apparatus disclosed in Japanese Patent Application No. 5-41448 (1993) comprises a terminal crimping unit and a wire conveying unit for feeding a coated wire to the terminal crimping unit.
The wire conveying unit includes a moving portion for moving the coated wire in a predetermined wire conveying direction, and a plurality of grasping portions spaced apart from each other in the wire conveying direction of the moving portion for grasping the coated wire at the near-end portion thereof. The coated wire grasped by the grasping portions has an intermediate portion sagging into a U-shaped configuration and opposite ends projecting in a direction crosswise to the wire conveying direction of the moving portion.
The terminal crimping unit is disposed to face the projecting ends of the coated wire, and includes a crimping portion for successively crimping crimp terminals to the ends of respective coated wires to fabricate wires to which terminals are crimped.
The crimp state of the crimp terminals crimped by the crimping portion influences the mechanical strength and electrical connection of the wires equipped with terminals and is subjected to strict quality control. For this reason, the height of a crimp portion (hereinafter referred to as "crimp height") of the wire barrel portion of the crimp terminal crimped to the core wire is conventionally measured to detect the crimp state of the crimp terminal.
Such a technique is disclosed, for example, in Japanese Unexamined Patent Publication No. 2-257001 (1990).
This patent publication states that a process for evaluating the crimp state by using the measurement value of the crimp height is relatively easy and has already been put into practical use.
The patent publication also states that the measurement of the crimp height by an operator with a micrometer results in low efficiency.
Thus, the prior art proposes a measuring tool installable in the aforesaid automatic wiring assembly fabricating apparatus. This measuring tool of the prior art includes an impingent stopper and a pair of side guides for positioning a terminal fitting relative to a measuring element; a terminal-crimped wire clamp lever for fixing the terminal-crimped wire; a fixing base having a width smaller than the width of a core wire crimp portion; and a clamp lever and a fixed clamp having inclined surfaces for clamping opposite sides of the core wire crimp portion.
The impingent stopper and side guides are, in plan view, substantially formed into a channel shape open to the tip of the terminal-crimped wire. The terminal-crimped wire clamp lever and the clamp lever are disposed to constantly oppose a core wire crimp portion fixing base and a terminal-crimped wire fixing base by a return spring. When the terminal-crimped wire is conveyed to the impingent stopper and side guides, these levers are operated to provide a spacing between the fixing bases and the levers, and then the terminal and the terminal-crimped wire are inserted into the spacing. Thereafter, the levers are released.
The aforesaid patent publication discloses the technique for causing the terminal-crimped wire to face the measuring element to fix the terminal-crimped wire to the measuring element, but does not disclose the technique for feeding the terminal-crimped wire to be measured to the measuring element. Therefore, the prior art is insufficient to achieve automatic measurement.
Specifically, the impingent stopper and side guides of the prior art are, in plan view, a channel shape open to the tip of the terminal-crimped wire. The terminal-crimped wire clamp lever and the clamp lever are disposed to constantly oppose the core wire crimp portion fixing base and the terminal-crimped wire fixing base by the return spring. Accordingly, it is necessary to cause the terminal-crimped wire to move longitudinally back and forth to position the terminal with respect to the impingent stopper and side guides. Therefore, if the automatic wiring assembly fabricating apparatus employs the measuring tool of the prior art, the grasping portions of the wire conveying unit must once release the terminal-crimped wire and grasp again the terminal-crimped wire after measurement with the grasping portions. The result is the need for inevitably re-holding the terminal-crimped wire when the terminal-crimped wire to be measured is conveyed to the measuring element and when the measured terminal-crimped wire is fed to the subsequent step. This results in complicated construction and control process of the automatic wiring assembly fabricating apparatus.
For the foregoing reason, there is a need for a device and method for measuring a crimp height which does not require the step of re-holding the terminal-crimped wire and hence can easily be applied to the automatic wiring assembly fabricating apparatus.